The effect of ascorbate and gibberellin application on some non-enzymatic mechanisms of savory (Satureja hortensis L.) under salinity stress conditions

Summer savory (Satureja hortensis L.) is a genus of aromatic plants of the family Lamiaceae. There are about 30 different species called savories, which summer savory and winter savory are the most important in cultivation. Satureja species are native to warm temperate regions and may be annual or perennial (Hadian et al., 2008; Rechinger, 1982). Soil salinity is one of the main environmental stresses affecting the growth of plants and their yield (Allakhverdiev et al., 2000). Adaptation of plants to environmental stresses such as salinity performs by accumulation of metabolites as carbohydrates and proline (Sanito di Toppy and Gabbrielli, 1999). Ascorbic acid is a powerful antioxidant that leads to inhibition of the free radicals by reduction (Fecht Christoffers et al., 2003). Gibberellins are commercial mushroom cultures obtained from pure and natural product known that used in plants. There are four types of GA; the best known is gibberellic acid which has positive effect on metabolites related to salinity tolerance (Hedden and Proebsting, 1999).
Material and Due to study the effect of salinity stress on some non-enzymatic mechanisms of savory under ascorbate and gibberellin application, a pot experiment was done in a greenhouse located in Pakdasht region and Islamic Azad University, Eslamshahr and Yadegar-e-Imam Khomeini (RAH) Shahre-rey Branchs in 2013. The experimental design consisted of a sixteen treatments, arranged as factorial based on completely randomized design with four replications, giving a total of 64 pots. Five-weeks old savory plants were sprayed with ascorbic acid (0 and 4 mM) and gibberellins
(0 and 4 mM) before inducing salinity stress with different concentrations of saline water
(0, 25, 50 and 75 millimolar). Control plants were sprayed with distilled water. Saline water was delivered to plants twice a week and last for three weeks. The proline by Bates et al (1973), Protein by Bradford (1976) and soluble and non soluble carbohydrates by Kochert (1978) were determined. The obtained data were subjected to analysis of variance using Duncan Multiple Range Test (P≤0.05) using SAS software.
The results showed that, with the exception of ascorbate effect on shoot soluble carbohydrates, the other main effects of experimental factors were significant on all non-enzymatic mechanisms of savory tolerance. So the intense salinity showed the highest decreased in physiological traits such as shoot and root protein (304.93 mg/L and 147.71 mg/L) and shoot and root non soluble carbohydrates (11.27 and 8.25) and improved shoot and root proline (27.46 mg/L and 16.52 mg/L) and shoot and root soluble carbohydrates (18.49 mg/l and 16.32 mg/l) to decrease the harmful effects of salt stress. The results revealed that only triple interaction effects of experimental factors were significant on shoot soluble carbohydrates and shoot and root non soluble carbohydrates and protein. So, the shoot soluble carbohydrates and Shoot and root proline content has 8.23, 1.92 and 3.73 manifold increase than control in 75 mM NaCl and ascorbate and gibberellin foliar application alternatively. Therefore it can be concluded that shoot soluble carbohydrates is the most main non-enzymatic mechanisms of salt tolerance in savory especially in ascorbate and gibberellins foliar application. Some reports indicated that ascobate increased proline content in bean and pea (Alqrainy, 2007) and okra (Baghizadeh et al., 2009) that are coordinate to our findings. Hoda et al (2010) revealed that GA improved both Shoot and root soluble and non soluble carbohydrates as the best and rapid non-enzymatic mechanisms of stress tolerance in citrus.
The results showed that salinity stress increased shoot and root soluble carbohydrates and proline and reduced shoot and root non soluble carbohydrates and protein. At the same time, spraying 4 ascorbate and 2 mM GA affected all associated non-enzymatic traits to salt stress resistance, however the additive effect of GA was more than ascorbate.